Ballistic computer



Jan. 18, 19 66 D. N. SPANGENBERG ET AL Filed June 22, 1962 BALLISTICCOMPUTER 7 Sheets-Sheet 1 I RUN-IN PULL-UP AIRCRAFT WIND AXIS 0 a L L 1:T AIRCRAFT-TO TARGE Fig. 4

INVENTORS DONALD N. SPANGENBERG WALTER GR YWACZ BY AGENT Jan. 18, 1966D. N. SPANGENBERG ETAL BALLISTIC COMPUTER Filed June 22, 1962 NEARZONE----- FAR ZONE '7 Sheets-Sheet 2 PUNCHED HOLE 2 MILES BEFORECHECKPOI/VT F ig. 2

INVENTORS DONALD N. SPANGENBERG WALTER GRZYWACZ ATTORNEY Jan. 18, 1966-D. N. SPANGENBERG ET AL 3,230,349

BALLIS'I'IC COMPUTER 7 Sheets-Sheet 5 Filed June 22, 1962 STEP CORRECT/ON rlllllll m S m z n N T C N A R W 0 W Y T N T 1.3% HA W D u A O l DRANGE WIND CORRECT/0N J Jan. 18, 1966 SPANGENBERG ET AL 3,230,349

BALLISTIC COMPUTER Filed June 22, 1962 '7 Sheets-Sheet 4 DRIFT ANGLEJan. 18, 1966 D, SPANGENBERG ETAL 3,230,349

BALLISTIC COMPUTER 7 Sheets-Sheet '7 Filed June 22, 1962 I I I l I I EIn gv LJ I I l I I I I i I G R i ON TE mm m s N D L A N O D WALTERGRZYWACZ BY AGENT United States Patent 3,230,349 BALLIS'HC CUMPUTERDonald N. Spangenberg and Walter Grzywacz, Southampton, Pa, assignors tothe United States of America as represented by the Secretary of the NavyFiled June 22, 1962, Ser. No. 294,650

11 (Ilaims. (Cl. 235--61.5)

(Granted under Title 35, US. Code (1952), sec. 266) The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

The present invention relates to a method and apparatus for improvingthe accuracy of low-altitude loft-bombing techniques, and moreparticularly to apparatus for providing navigational assistance to thepilot of a high performance aircraft while approaching a bombing targetat a low altitude, for providing aircraft maneuvering and pull-upguidance to the pilot before release of a bomb, and for providingautomatic release of the bomb to produce precise delivery of the bombabove or on a selected target.

Military requirements for effecting an aerial bombing mission,especially where nuclear weapons are involved, demand that the missilebe delivered at the target with suflicient accuracy to accomplish themission, that an adequate margin of safety from the effects of theweapon blast be provided for the aircraft, and that the element ofsurprise to the enemy be maintained. Loft-bombing was developed as onetechnique for fulfilling these requirements. The loft-bombing techniquebegins with the aircraft on a horizontal approach or run-in toward thetarget at tree-top level to avoid detection by enemy radar. At somediscrete distance from the target, the pilot applies full throttle andpulls back on the control stick thereby pulling the nose of the aircraftup from level flight. This maneuver is called pull-up. When the aircraftlongitudinal axis forms a predetermined angle with the horizontal plane,the bomb is manually or automatically released. The momentum andattitude of the bomb at release causes the bomb to begin its trajectoryupward, and then descend.

One such known loft-bombing technique is partially mechanized in anattempt to reduce the demands on pilot participation and to increase theeffectiveness of a loft bombing mission. On the way to the target, thepilot must recognize a landmark known as the initial point, or IP, whichis of known geographical location with re spect to the target. Based oncertain assumed flight parameters for the run-in and pull-up maneuvers,a bombing problem computed prior to the mission begins at the IP. Sothat the actual flight parameters are consistent with those assumed forthe problem, the pilot must position his aircraft over the IP at a fixedvelocity and course. Upon crossing the IF, the pilot starts a timerwhich measures a precomputed time interval representing run-in distancefrom the IP to a precomputed pull-up. At the end of the time interval, acommand signal is presented to the pilot to maneuver the aircraft in ahalf Cuban eight. At the beginning of the pull-up portion of thismaneuver, there is an increase of centripetal acceleration or g-loadingalong the aircraft Z-axis from the l-g present at horizontal flight to4-gs in about two seconds. The g-level transition is made lineardepending upon the best estimate of the pilot as he executes pull-up.After the two-second period, the pilot holds the centripetalacceleration at 4-gs until the aircraft completes a little more thanone-half of the loop and then the pilot begins aircraft roll-out. Duringthe pull-up portion, when the aircrafts pitch angle corresponds with apreselected angle, the bomb is automatically released.

"Ice

The requirements essential for a successful mission utilizing such aloft-bombing technique are numerous. First, there is an extremely highdependence placed upon the accuracy of navigation after positiverecognition of the IP. Failure to recognize the IP will result in anaborted mission or in an over the-shoulder delivery as a last resort.Second, the positioning of a high-performance aircraft flying at lowaltitude over a fixed point, on a fixed course, and at a fixed highspeed requires great skill of the pilot. Third, a constant, high speedrun-in to the target must be maintained. Fourth, the rate of thetransition of g-loading in the two-second period must be consistent withthe precomputed estimates. And fifth, no accumulated errors during theentire bombing maneuver are permissible because the preset bomb releaseangle commits the pilot in advance to the assumed flight parameters.Restated briefly, the known loft bombing techniques allowed for nodeviation from the severe requirements in flight conditions dictated bythose assumed in the precomputed bombing problem.

Accordingly, it is an object of the present invention to provideapparatus for increasing the reliability and accuracy of theloft-bombing technique but at the same time lessen the demands on pilotjudgment, with which variations in the pertinent flight parameters canbe compensated for prior to and during the run-in. maneuver of theloft-bombing mission, with which the point of start of pull-up followingthe run-in is automatically computed from the pertinent flightconditions existing during run-in, with which the angle of bomb releaseduring pull-up is automatically computed during the pull-up, and withwhich the transverse acceleration transition during pull-up isprogrammed based on an on-course distance.

It is another object of the present invention to provide a navigationalaid to the pilot in which the instantaneous position of the aircraft isdisplayed in the cockpit by a cursor and a map each moving in proportionto a computed ground speed and in which synchronization of cursor andmap motion can be corrected at preselected ground check points havingcorresponding marks on the map.

Still another object of the present invention is to provide apparatusfor the computation of guidance information and presentation thereof tothe pilot for steering the aircraft to a desired destination and fororienting the aircraft into a prescribed attitude for pull-up.

And still another object of the present invention is to provideapparatus for low-altitude loft-bombing which employs a visualdead-reckoning type strip-map display of an approach corridor leading toa target and has navigational capabilities, with which the displaycontinuously presents a computed ground position of an aircraft, withwhich the computed ground position accuracy is refined by computeddisplacement and rate corrections, with which reliability ofloft-bombing is further enhanced by the presentation of a computedsteering angle dictating the change in aircraft heading required todirect the aircraft ground track toward the target, and with which thecomputations to effect these presentations requires inputs from trueairspeed, magnetic compass heading, and map display synchronization bythe pilot at two or more preselected ground check points also shown onthe map.

A further object of the present invention is to lessen the demand forpilot acuity by providing apparatus permitting a relatively widelatitude :of deviation in approach to the target, with whichnavigational aid during approach to the target is improved, with whichpull-up point varies in accordance with variations in certain flightconditions during the approach, with which the transverse accelerationschedule is programmed during the pull-up, with which visible andaudible warning signals are presented to the pilot for executingaircraft maneuvers, and in which the bomb release angle varies inaccordance with ballistic computations.

Various other objects and advantages will appear from the followingdescription of one embodiment of the invention, and the most novelfeatures will be particularly pointed out hereinafter in connection withthe appended claims.

In the drawings:

FIG. 1 diagrammatically represents profiles of the flight path of anaircraft and the trajectory of a bomb released from the aircraft on alow-altitude loft-bombing mission;

FIG. 2 represents a strip map of the present invention which depicts atypical approach corridor leading to a target of a loft-bombing mission;

FIGS.3a, 3b, and 3c schematically represent an approach computer andnavigational display of the present invention;

FIG. 4 diagrammatically represents a top plan view of an aircraft on alow-altitude loft-bombing mission; and

FIG. 5 schematically represents a ballistic computer of the presentinvention.

FIG. 6 schematically represents an alternate embodiment of the computer.

In the illustrated embodiment of the invention, a lowaltitudeloft-bombing mission is best described with particular reference toFIG. 1. An aircraft 10 approaches the target T from the left beginningon a horizontal runin path 11 when it crosses the start point S. Theaircraft 10 is maintained at a relatively low altitude to avoid thepossibility of detection by enemy radar until reaching a pull-up point12. The aircraft 10 then takes an insidelooped pull-up path 13 duringwhich the aircraft 10 experiences a transition in centripetalacceleration along its vertical or Z-axis from l-g in horizontal flightto a predetermined higher level. The change in acceleration isprogrammed against distance to the target T, and when the aircraft 10attains a computed upward pitch angle 0 such as at the point 14 on thepull-up path 13, a bomb is released. After bomb release, the aircraft 10continues on the inside loop maneuver and then half-rolling, to directthe aircraft 10 in an upright attitude in the general direction of thestart point S. The bomb, being in free flight from the release point 14,is lofted to an apogee 16 and then it descends toward the target T alongthe trajectory 17.

Several important factors affect the trajectory 17 in a loft bombingmission. One factor is run-in speed. For example, for a constant pull-uppoint 12, an excessive run in speed will cause a lofted bomb toovershoot the target T while a lower run-in speed may cause the bomb tostrike short of the target T. The present invention contemplatescompensation for different run-in speeds by varying the position of thepull-up point along the run-in path 11.

Another factor is wind. In the consideration of wind, it is convenientto resolve its velocity vector into components parallel and normal tothe length of the approach corridor and hereinafter referred to as rangewind and cross wind, respectively. Each has the effect of decreasingbombing accuracy but in different ways. Range wind has the effect ofdistorting both the pull-up path 13 and the trajectory 7 from what it isin still air. The distortion for a range Wind in the same direction asthe flight, or a tail wind, is elongation, While a head wind producescompression. The present invention further contemplates compensation forsuch distortions by shifting the pull-up point 12 farther from or nearerto the target T.

Still another factor affecting the trajectory 17 is Weight. Duringpull-up, a heavy aircraft moves in a tighter loop and fall-off ofvelocity is relatively fast. The aircraft 10 would also be farther fromthe target T when the release point 14 is reached. Hence, the releaseangle 0 should be decreased for a heavier aircraft to extend the rangeof the trajectory 17. On the other hand, a light airplane moves in alooser loop and would have a higher velocity at the release point 14since the velocity fall-off would not be as great. The aircraft 10 wouldalso be closer to the target T when the release point 14 is reached.Hence, the angle of release 6 at the release point 14 should beincreased for lighter aircraft to shorten the range of the trajectory17.

Available thrust at the pull-up point 14 is another factor which affectsthe trajectory 17. Because of the decrease in thermodynamic efficiencyof an aircraft engine on a hot day, less thrust would be availableduring the pull-up maneuver. The effect of lower atmospheric pressure onthe trajectory 17 is comparable to the effect of higher temperature.Hence a tighter loop, less advance down range, and a greater fall-01f invelocity results. The added drag resulting from the increased angle ofattack necessitated by a lower atmospheric pressure also lowers the netthrust available. To compensate for the change in thrust, modificationof the release angle 0 accordingly is contemplated.

Finally, there is the factor of run-in altitude. For example, a higheraltitude will produce an overshoot of the bomb relative to the target T.Thus, for higher altitudes, shifting of the pull-up point 12 fartherfrom the target T is contemplated.

The strip map indicated generally by the numeral 20 in FIG. 2 representsan aerial view of a typical loft-bombing approach corridor from thestart point S to the target T. For purposes of explanation only, andwithout limiting the invention to any specific example, the total lengthof the corridor defined between the start point S and the target T isarbitrarily shown as 60 miles. A mean course line, hereinafteridentified as the MCL, drawn end-to-end and through the center of thecorridor is an arbitrarily selected azimuth coinciding with the desireddirection of approach to the target but about which the aircraft 10 maydeviate within the lateral limits of the strip map 20. The 60-mileapproach corridor shown in the map 20 is divided along its length intotwo zones, namely, the FAR ZONE and the NEAR ZONE. The FAR ZONE beginsat the start point S 60 miles from the target T and extends to adistance 15 miles from the target T, then the NEAR ZONE continues to thetarget T. The map scale or reduction in map size in the FAR ZONE isarbitrarily chosen in this embodiment as three times the scale orreduction in map size in the NEAR ZONE.

The map 20 is prepared prior to a loft bombing mission from intelligenceinformation gathered on the area surrounding the target T. There may beseveral maps prepared and loaded in individual cartridges for use in theinvention to cover the eventuality of an alternate approach to thetarget T or even of an alternate target. On a mission, the pilot maycarry several map cartridges from which a selection can be mademomentarily according to the tactical situation encountered.

The target T in the illustrated example is a cluster of storage tanks asshown by the insert circular picture pointed toward the target T.Principal towns, major highways, railroads and rivers are plotted on themap 20 with many minor features and landmarks omitted to avoidcluttering and to facilitate rapid reading by the pilot.

Numerous check points identified by the circled numbers 1, 2, 3, 4 and 5are interspersed along the approach corridor to be used for navigationaland ballistic computations. Accompanying each check point is an insetcircularpicture of an object serving as a precise point of reference inthe approach corridor. The object at each check point is selected forits easily recognizable features and has a known position with respectto the target T.

The map 20 contains several additional visual aids for the pilot. Besideprincipal terrain and geographical features, there are tick marks alongthe MCL designating oncourse distances to the target T. Beginning aroundthe 45-mile tick mark, there is a shaded area 21 on each side of the map20 to warn the pilot of a pending change of map scale and a narrowing ofthe approach corridor. It

is necessary for the pilot to navigate the aircraft between the shadedareas 21 by the time that the -mile tick mark is reached when the mapchanges scale. In the NEAR ZONE there are two curved lines 22symmetrical about the MCL and beginning at opposite sides of the map 20about 9 miles from the target T. The curved lines 22 form a funnel-likearea narrowing toward a pull-up region 23, shown shaded. The curvedlines 22 represent limits from which the pilot can still maneuver theaircraft 16 into position for pull-up by executing two standard rateturns, i.e. the rate of change in heading need not exceed 3 degrees persecond. The pull-up region 23 represents the on-course limits forballistic computations and lateral tolerances. The size of the pull-upregion 23 is indicative of the degree of flexibility provided by theinvention for the execution of a loft-bombing mission.

The map 20 is displayed in the aircraft 10 on a cartridge insertable ina display unit 26, as shown in FIG. 30, and is transported by a sprocketroller 27 in a direction parallel to the MCL. The map 20 has punchedholes 28 spaced along each side for engaging spurs in the sprocketroller 27. A roller knob 29 fixed at one end of the roller 27 providesmanual slewing of the map 20 to any desired position along the MCL. Itis contemplated that map slewing may also be accomplished electricallyby additional push buttons and electrical relays.

A transparent cursor 31 in the display unit 26 provides a continuousindication of the lateral position of the aircraft 10 in the approachcorridor. The cursor 31 has a vertical index 32 inscribed thereon withtick marks spaced at intervals corresponding to each of the scales ofthe map 29. A transparent bar 33 fixed against motion on the displayunit 26 in front of the map 21 has a horizontal index 34 inscribedthereon with appropriately spaced tick marks. The point on the map 20under the intersection of the vertical and horizontal indices 32 and 34is a computed instantaneous map position. The cursor 31 is drivenlaterally by means of a worm gear 36 which is rotatably supported at itsends in the display unit 26 by means not shown.

NAVIGATION COMPUTATIONS The point on the map which appears at theintersection of the vertical and horizontal indices of the display unit26 is determined by navigational computations which may be categorizedgenerally as ton-course and cross-course computations. The on-coursecomputation determines the position of the map along the MCL withrespect to the horizontal index 34. The cross-course computationdetermines the position of the cursor 31 along the horizontal index 34relative to the MCL.

Oil-course map drive The on-course computation mainly consists of anintegration of true airspeed TAS which yields an on-course distancemeasured from the start point S. The TAS input is derived from atransducer 37, such as a pitot tube having its pressures transformedinto an angular position on a shaft 38. The shaft 38 is connected to oneinput of a mechanical differential 39. If the other input to thedifferential 39 is locked, the output shaft 41 is also proportional tothe TAS and positions the rotor of a linear transformer 42 in a mappositioner unit 4th A linear transformer, as used herein, has thecharacteristic of generating an output voltage whose magnitude in alinear function of an input shaft position. The output voltage oftransformer 42 is connected to an on-course integrator comprising acombination of a motor 44, a generator 46 and an amplifier 47. The otherinput of the differential 39 being locked, the position of a shaft 48between the motor 44 and the generator 46 is a time integral of the TAS.The shaft 48 also connects to the rotor of a synchro transmitter 49 of amap drive unit 50 through one input of a mechanical differential 52 anda differential output shaft 53. Depending upon the position of a scalechange switch 57a operated by a cam 57 driven by the shaft 61 when themap 20 indicates the aircraft position is 15 miles from the target T,either a FAR ZONE synchro receiver 56 or a NEAR ZONE synchro receiver 54will supply a voltage to an amplifier 58 to drive a map drive motor 59.An output shaft 61 of the motor 59 is selectively connected to thesprocket roller 2'7 in the map display unit 26 through a clutch 62 whichis engaged when the map 20 is inserted. The shaft 61 is also coupled tothe rotors of the receivers 54 and 56 thus providing a continuousfollow-up of map position through the receiver 54 or 56 as determined bythe switch 57a. The coupling between the rotor of the receiver 54 andthe shaft 61 includes gears 63, so that the map drive rotor 61 isrequired to drive through three times the angular displacement of theshaft 53 in order to follow-up a given increment of error voltage at theamplifier 58. This corresponds to the map scale change.

Due to the presence of a range wind, an error will accumulate betweenthe actual ground position of the aircraft 10 and the position indicatedon the map 20 inasmuch as TAS measurement is not a measurement of groundspeed of the aircraft. In order to align the map position with aircraftposition relative to the ground and synchronize the map drive speed withaircraft ground speed, several adjustments are necessary to the shaft 53at the input of synchro transmitter 49 of the map drive unit 50. One ismodification of the shaft 43 at the input of the map positioner unit 40in the form of a step correction. The step correction periodicallyrepositions the map 20 so that a point under the horizontal index 34corresponds with the actual position of the aircraft over the ground inthe approach corridor. Another .is a modification of the shaft 33 at theinput of the map positioner unit 40 in the form of a rate correction.

On-course step correction Step correction is a periodic skipping of themap 20 either in the forward or reverse direction. This occurs at anytime there is a lack of agreement between the position at one of thecheck points 1, 2, 3, 4 or 5 relative to the horizontal index 34 and thelocation of a corresponding object on the ground at the time the pilotmakes a visual comparison and effectuates synchronization. A stepcorrection unit 69, operating independently of rate correction, and inboth the NEAR and FAR ZONES, restores alignment. At an on-coursedistance of two miles before and after each check point called theenabling zone, an electrical enabling switch 67 fixed on the displayunit 26 operates. The switch 67 has two opposing contacts held apartbecause they extend on the opposite surfaces of the map 20.Corresponding to precisely 2 miles before each check point 1, 2, 3, 4and 5 on the map 20, there is a hole 68 laterally aligned with contactsof the enabling switch 67. When the map 20 moves so that one of theholes 68 is between the contacts of the enabling switch 67, the contacts close and cause a solenoid operated clutch 69 to engage therebycausing the rotation of the map drive output shaft 61 to be transmittedto the rotor of a linear transformer 66. By appropriate relays, contact67a also moves from the position illustrated to connect transformer 66in series with a linear transformer 76 and an amplifier 71. As map driveprogresses, an output voltage of the transformer 66 appearing at theamplifier 71 and representing a distance error, decreases from a presetlevel at the step correction enabling position (2 miles before the checkpoint) to zero at the check point and then increases in the oppositedirection to the same level at the step correction disabling position (2miles after the check point). A motor 72 driven by the amplifier 71 hasits output shaft 73 selectively connected to another input of themechanical differential 52 through a solenoid operated clutch '74.Positive positioning of the motor 72 is accomplished by followup of thelinear transformer 76. The clutch 74 is disengaged while the distanceerror is accumulating on the output shaft 73. The pilot depresses a MARKbutton '7 '77 located on the display unit 26 when he observes that theaircraft is abreast of a check point. By an electrical circuit, notshown, a contact 77a in the step correction unit 60 moves from theposition illustrated to connect the transformer 76 as the sole input tothe amplifier 71, and the motor 72 Will drive until the transformer 76has been restored to its position at the start of step correction. TheMARK button 77 also causes clutch 74 to engage so that the restoringrotation appearing on the shaft 73 is transmitted to the other input ofthe mechanical differential 52. The input on shaft 48 to thedifferential 52 is thus periodically corrected by the increment ofrotation entered through the shaft 73. Depressing the MARK button 77also disengages the clutch 69 previously engaged by the switch 67.'C'am' switch 70 will disengage the clutch 69 at the end of the enablingzone if the MARK button 77 is depressed at a check point. A fly-backspring 79 restores the rotor of transformer 66 to the step correctionenabling position.

Summarizing step correction, when the aircraft 10 comes abreast of eachpreselected check point the MARK button 77 is depressed. If, at thatinstant, the on-course component of the map position does not agree withthat of the georgraphical position of the aircraft 10, that is, if thecorresponding check point on the map is not under the horizontal index34, the map will skip due to the restoring motion on the shaft 73 anamount suificient to align the map with the geography. It should benoted that failure to depress the MARK button 77 Within the enablingzone will not be harmful to the accuracy of the existing map alignment.Tracking will continue in accordance with the corrected informationaccumulated up to the previous check point.

Step correction can be made in both the NEAR and FAR ZONES. Alocked-rotor linear transformer 81 in the step correction unit 64 havinga voltage transformation ratio corresponding to the change in map scaleis selectively connected in the circuit with transformer 66 by contacts57b which are operated at miles from the target T by the cam 57.

Orr-course rate correction On-course rate correction refers to thedifference or error between the map drive rate and the actual aircraftground speed. So that the drive rate is accurately synchronized with theground speed of the aircraft 10, this error must be taken into account.This is accomplished before the aircraft 10 reaches the NEAR ZONE. Ineffect, the on-course rate error, prior to any correction. is thedifference between the true airspeed TAS and ground speed. Thisdifference or on-course rate error is added through the other input ofthe mechanical differential 39 to modify the TAS signal on shaft 38whereby the position of the output shaft 41 is a corrected TAScorresponding to the on-course ground speed. The oncourse ratecorrection is computed within the enabling zone by an on-course ratecorrection unit 90.

To obtain the correction rate, an increment of map transport distance isdivided by the time from start point 5. A timer 86 produces a positionon a shaft 87 which is a function of time from the start point S. Theshaft 87 drives the rotor of a linear transformer 88 through a solenoidoperated clutch 89. Clutch 89 is engaged at the start of the run-in whena START button 80 is depressed. At the beginning of the enabling zone (2miles before each check point in the FAR ZONE) when the enabling switch67 engages the clutch 69, map motion is transmitted through the outputshaft 61 to the rotor of a linear ransformer 95. Within the enablingzone a contact 67b, operated by the enabling switch 67, connects theelectrical output of the linear transformer 88 to the rotor coil of alinear transformer 91. The fixed coil of the transformer 91 is connectedin series with a contact 670, operated by the enabling switch 67, to thefixed coil of the transformer 95, and an amplifier 92. The resultingvoltage at the amplifier 92 is proportional to the quotient of theelectrical signals developed by transformers 88 and 95. locked rotor ofthe linear transformer 94 which has its electrical output connected tothe rotor coil of transformer 95. A motor 93 is driven by the amplifier92 accordingly positioning an output shaft 96. Follow-up for the shaft96 is provided by its connection to the rotor of the transformer 91. Theangular position of the shaft 96 at any instant within the enabling zoneis representative of the instantaneous rate error which is the negativeof the amount that would be necessary to correct the map drive rate; andwhen the pilot depresses the MARK button 77 in an enabling zone, acontact 771) disconnests" transformer 95 and'le'aves transformer 91 asthe sole input to the amplifier 92. Simultaneously, a solenoidoperatedclutch 97 engages the shaft 96 to the other input of the differential 39through a shaft 96a. As the motor 93 restores the rotor of transformer91 back to the null position, the restoring rotation of the shaft 96 istransmitted through the clutch 97 to the differential 39 where itmodifies the TAS input on the shaft 38 as appears on the shaft 41 to themap positioner unit 40. In a manner described above, clutch 69disengages at the end of the enabling zone, and the fly-back spring 79restores the rotor of transformer 95 to its initial position. Similarly,at the end of a loft-bombing mission the clutch 89 disengages and afly-back spring 98 restores the rotor of transformer 88 to its initialposition.

It will be noted that on-course rate correction is provided for onlywithin the FAR ZONE, whereas step correction is accounted for in boththe NEAR and FAR ZONES.

Cross-course cursor drive To facilitate an understanding of the anglesrelated to cross-course navigation, particular reference will be made toFIG. 4. A medial line identified as a mean course line or MCL on the map20 corresponds to a magnetic rhumb line extending end-to-end along theapproach corridor to the target T. Due to the presence of thecrosscourse component of wind and due to the probable lateraldisplacement of the aircraft 10 from the MCL, various angles can bedefined. For a lateral displacement y, a target angle 1- is formed by anaircraft-to-target line and the MCL. Assuming a cross wind componentfrom the left side of the approach corridor, or downward in FIG. 4, theaircraft it must take a port heading. The angle 1; formed by thelongitudinal axis of the aircraft 10 and the MCL is the aircraft headingrelative to the MCL. The path of the aircraft 10 actually taken over theground is called the ground track and defines a course angle 0: with theMCL, The difference between the heading angle and the course angle 06 isa drift navigational angle 6 and the angle formed by the ground trackand the aircraft-to-target line is the steering angle 0'.

The distance the aircraft 10 is from the target T along theaircraft-to-target line is the actual distance-to-go. For small targetangles r, the actual distance-to-go is substantially equal to theon-course distance-to-go as measured along the MCL.

The cross-course cursor 31 position is the result of integration of across-course component of the ground speed from an initial lateralposition of the lateral cursor 31 to a subsequent lateral position. Theinitial position is considered as a constant of integration for thepurpose of computation. The product of the TAS and the course angle 0:is further considered to be a close approximation of the cross-coursecomponent of ground speed because, for small course angles a, the sineof at is substantially equal to the angle on in radians. Inasmuch asnavigation within the approach corridor usually involves course anglesat which are less than 15 degrees, this approximation of the sine can bemade without significant loss in accuracy.

Appropriate scale factoring is provided by the The cursor 31 in thedisplay unit 26 continuously tracks the lateral position of the aircraftby means of a cursor drive unit 100 (FIG. 30). True airspeed TAS,appearing as an angular position on shaft 38 is connected to the rotorof a linear transformer 101. The output voltage excites the rotor coilof a linear transformer 102 which has its rotor positioned by a shaft105 which is angularly positioned as a function of the course angle a.The manner in which the course angle a is obtained on the shaft 105 willbe described below in connection with drift correctoin. The outputvoltage developed in the fixed coil of the transformer 102 thus becomesthe product of TAS and the course angle a which is substantially thecross-course component of ground speed. This voltage is fed to thecross-course integrator which includes a generator 103, an amplifier104, and a motor 106. An output shaft 107 of the motor 106 is positionedas a function of a time integral of the cross-course ground speed,namely, the cross-course distance. The position of shaft 107 is thentransformed into an electrical voltage by means of a linear transformer108. The output voltage of the transformer 103 is connected throughcontacts 80a and 800 in series with linear transformers 109 and 112across an amplifier 111 when the START button 80 is depressed. Theamplifier 111 drives a cursor drive motor 113 which is drivinglyconnected to the worm gear 36 by an output shaft 114. The shaft 114 isalso coupled to the rotor of the linear transformer 109 for follow-upaction. The motor 113 continues to drive until the change in outputvoltage of the transformer 10% is equal and opposite to the change inoutput voltage of the transformer 108. The position of the shaft 114 istherefore representative of the cross-course distance traveled duringthe integration. Another pair of contacts 80b, operated by the STARTbutton 80, are maintained in the position illustrated until the aircraft10 is abreast of the start point S. This is so that cursor 31 can beplaced at a given initial lateral displacement from the MCL and somaintained until integration is desired.

For establishing the lateral position of the vertical index 32 relativeto the map so that it corresponds to the lateral position on the groundthroughout the run-in, it is necessary to set the vertical index 32 on acorresponding ground reference point from which the distance integrationis started. This is accomplished by the linear transformer 112 whichprovides for manually setting the initial lateral cursor position, orsubsequent lateral positions. From a mathematical standpoint, thesetting may be regarded as fixing the constant of integration. Manualsetting of the cursor is made at any time by a cursor adjusting knob 116which turns the rotor of the transformer 112 through a shaft 117. Manualadjustments can also be made prior to depressing the START button 80,whereby contacts 80a and 80!) remain in the positions illustrated. Thus,transformers 105' and 112 are the only inputs to the amplifier 111. Theposition of the shaft 114 therefore corresponds to the lateral positionselected on the knob 116. When the aircraft 10 is over the groundreference point, the START button 80 is depressed whereby contacts 80a,80b and 800 enable rotation of the shaft 114. At 15 miles from thetarget T, a linear transformer 118 having a locked rotor has the outputof its fixed coil connected to the rotor coil of transformer 109. Therotor of transformer 118 is locked in a position which yields atransformation ratio equal to the scale change from the PAR ZONE to theNEAR ZONE.

Drift correction The course angle at appearing as an angular position onthe input shaft 105 of the cursor drive unit is computed byalgebraically adding the heading angle 1; and the drift angle 6. Thelatter is computed in a drift angle unit 120 by components of a lateralerror due to a cross wind and the on-course distance over which thelateral error accumulated. The lateral error, which is the cross-coursedistance in miles between one point on the map 20 corresponding to theactual ground position of the aircraft 10 and another point on map 20indicated by the vertical index 32, is manually introduced in the driftangle unit 120 at the knob 116 connected by the shaft 117 and a solenoidoperated clutch 125 to the rotor of a linear transformer 124. Thepositioning of the vertical index 32 is based solely on the bestestimate of the pilot. The output voltage of the transformer 124,proportional to the lateral error, is connected to the one stator coilof a resolver 126. The second stator coil of the resolver 126, inquadrature with the first stator coil, is supplied by the output voltagefrom a linear transformer 127. The angular position of the output shaft61, representing the oncourse distance since the previous lateral checkpoint, is connected to the rotor of the transformer 127 through thesolenoid operated clutch 128. The clutches 125 and 128 are engaged bydepressing the START button thereby transmitting the angular positioningof shafts 61 and 117 to the transformers 127 and 124, respectively. Theresolver 126 has one of its rotor coils (not shown) short circuited,while the other rotor coil is connected to the input of an amplifier 129which drives a motor 131 when contacts 80d, operated by the button 80,move from the position illustrated to the opposite position. An outputshaft 132 of the motor 131 provides a follow-up connection between therotor of the resolver 126 and the motor 131. The angular position on theshaft 132 therefore is the negative of the drift angle 6 whose tangentis the lateral error divided by the on-course distance in which thelateral error was accumulated.

A DRIFT button 122, located on the display unit 26, is depressed when aselected lateral reference is reached. Clutches 125 and 128 disengageallowing fly-back springs 123 and 123:: to restore the rotors of thetransformers 124 and 127 to their initial or zero position. Contacts122a then move from the position illustrated to the opposite positionallowing the motor 131 to drive the resolver 126 back to its initial orZero position. A normally engaged clutch 133, which disengages when theSTART button 80 is depressed and permits shaft 132 to be positioned bythe inputs of shafts 117 and 61 without affecting a mechanicaldifferential 134, reengages when the DRIFT button 122 is depressedthereby transmitting the restoring rotation of the shaft 132 to oneinput of the differential 134.

The drift angle unit also includes an option for the pilot to set anestimated cross wind into the system prior to the start of the run-in ofa bombing mission. A CROSS WIND knob 148 positions the rotor of a lineartransformer 149 having a stator coil connected in series with the statorcoil of a linear transformer 151, contacts 20d in the position shown,and the amplifier 129 to drive the motor 1131. Being normally engaged bythe clutch 133 prior to start, the shaft 132 drives the transformer 151until a voltage has been developed in the stator coil of the transformer151 which is equal and opposite to the output voltage of the transformer149. The position of the shaft 132 thus represents the initiallyestimated cross wind as a drift angle 5, at an assumed oncourse TAS.After the START button 80 is depressed, the electrical circuit in thedrift angle unit 120 is changed so that manual setting of cross wind isno longer operative. Initially, the transformer 151 is rotated to aposition which is representative of the initial cross wind drift angle.Clutch 133 is disengaged when the START button 80 is depressed and isengaged at the completion of the drift computation. It will be notedthat successive drift solutions are added to the initial cross winddrift angle existing on the transformer 151 and are stored for futureuse.

The drift angle 6 at the shaft 132 is combined with an aircraft heading7 relative to the MCL at the mechanical differential 134. If more thanone increment of drift which in turn drives a motor 146.

angle has been computed, the correcting quantity at the differential 134is a summation thereof.

Course angle A heading unit 140 computes the aircraft heading 1; withrespect to the MCL. Map angle A (FIG. 4) with respect to North and localmagnetic variation angle at the target T are set into the heading unit140 by means of adjusting knobs 137 and 138, respectively. The summationof these two quantities takes place in a mechanical differential 139with its output shaft 136 representing the magnetic azimuth [3 of theMCL. The rotor of a differential generator 141 is coupled to the shaft136 and is continuously excited by a signal from a magnetic compass 145in the aircraft 10. The output signal of the generator 141 is thedifference between the magnetic heading ,u and the magnetic azimuth [3of the MCL, or the aircraft heading 7 with respect to the MCL. Theheading 1; is then transmitted to a control transformer 143 which hasits output voltage connected to an amplifier 144 The shaft 147 of themotor 14-6 is mechanically coupled to the rotor of the transformer 143to provide follow-up. Thus, the angular position of the shaft 147 isrepresentative of the aircraft heading 17 with respect to the MCL. For ano-drift condition, this angle 1 is also the course angle a. The heading1 on shaft 147 and the drift angle on shaft 132 are algebraicallycombined in the differential 134 to produce the course angle a on theshaft 1115. As noted previously, the course angle at modifies the TASsignal on shaft 38 in the cursor drive unit 161) to obtain thecross-course speed component for driving the cursor 31.

Steering angle The above-described mechanisms provide a display on themap 2% of the aircraft instantaneous position relative to ground by theintersection of the horizontal index 34 and the vertical index 32 withinthe approach corridor to the target T. The line generated by themovement of the instantaneous position is called a ground track. Anadditional important navigational aid to the pilot is a steering angle0' (FIG. 4). The steering angle 0' enables the pilot to direct theground track of the aircraft 10 toward the target T, so that the groundtrack coincides with the aircraft-to-target line. The steering angle 0'is derived by a steering angle unit 160 using as inputs, the lateraldistance y from the MCL, the on-course distance to the target T, and thecourse angle a. The oncourse distance to the target T is introduced bydisplacing the rotor of a NEAR ZONE linear transformer 156 and a FARZONE linear transformer 157 an amount equal to the scale distance fromthe target T to the start point S. This may be accomplished by firstinserting the map 20 into the display unit 26 so that the target T liesunder the horizontal index 34, engaging the clutch 62, and then slewingor transporting the map 20 manually by the knob 29 until the start pointS lies under the horizontal index 34. Because the clutch 62 is engaged,the rotors of the transformers 156 and 157 will rotate by theirconnection through the shaft 61. This operation stores adistance-to-target in the rotor position of the transformers 156 and157. As the aircraft approaches the target T along the approachcorridor, the map drive motor 59 is continuously reducing the value ofthe stored distanc-e-to-target. The output voltage of the transformers156 and 157 are selectively supplied the first stator coil of a resolver159 through a contact 57 operated by the map scale changing cam 57 at 15miles from the target T. The electrical signal applied to the secondstator coil, in quadrature with the first, comes from the output of alinear transformer 161 which has its rotor positioned by the shaft 114from the cursor drive unit 100, and therefore represents the lateraldisplacement y from the MCL. One rotor coil (not shown) of the resolver159 is short-circuited, while the other rotor coil supplies a "oltage toan amplifier 162 which drives a motor 163. The motor 163 is mechanicallycoupled to the rotor of the resolver 159 by a shaft 164 forpositive-positioning follow-up. The resulting angular position of theoutput shaft 164 represents a target angle 7- whose tangent is thequotient of the lateral distance y from the NCL divided by the on-coursedistance to the target T.

The target angle 7 and the course angle 06 are the inputs to amechanical differential 166 which algebraically combines the courseangle oz and the target angle 7, the output on a shaft being thesteering angle a. If the course angle a equals the target angle r, inboth magnitude and direction, the ground track of the aircraft 10 passesthrough the target T. If the two angles are not equal, the differencerepresents an angle which the pilot must apply as a steering correctionin order to direct the ground track of the aircraft toward the target T.The steering angle 7 is converted into an electrical signal by apotentiometer 167 and is displayed to the pilot on a vertical point-er168 of a cross needle indicator 179. It should be noted that thesteering angle 0' is merely a reference. The pilot may deviate theaircraft 111 laterally along the approach corridor to suit conditions ofthe bombing mission. Only during the last portion of runin, that isimmediately prior to the pull-up point 12, must the steering angle 0' becorrected so that the aircraft ground track coincides with theaircraft-to-target line. At one-third of a mile before the pull-up point12, a G-start selector switch 171 moves from the position illustrated todisconnect the steering angle unit 161 from the indicator and to connectthe output from a yaw/roll unit 175. The shaft inputs 173 and 174 to theunit 175 represent yaw and roll signals from byros in the aircraft 10and by arrangement of potentiometers in the unit 175, a combined rolland yaw signal is connected to the indicator 1763 to produce deflectionof the vertical pointer 168 during pull-up. The indicator 170 alsoincludes a horizontal pointer 176 electrically connected to apotentiometer 177 which is varied by a mechanical output of anaccelerometer 178. The accelerometer 178 is responsive to accelerationthrough the transverse axis or Z-axis of the aircraft 10.

BALLISTICS COMPUTATIONS The ballistic system of the present invention isprincipally a mechanical analog computer integrally a part of thenavigational computer system, sharing its components and utilizing camsto solve the bombing problem. The navigational system as above-describedprovides a convenient stepping stone leading to a coordinated ballisticcomputation system insofar as it provides the necessary parameters forcomputing a variable pull-up point and a release angle for the bomb inthe bombing problem. The availability of these parameters in thenavigational system of the present invention allows the solution of theballistic problem with only small structural additions. For example,navigational computation of the distanceto-target, together with TAS,can determine a variable pull-up point; and a parameter of wind permitfurther refinement of the pull-up point.

Prior to reaching the pull-up point 12, a wind correction and a stillair pull-up distance are developed and combined to obtain a pull-uppoint which will vary in accordance with the input parameters. After thepull-up point 12, the g-level transition in the pull-up maneuver isprogrammed for the pilot and the bomb release angle is automaticallycomputed in accordance with the errors accumulated from the pull-uppoint 12 to the release point 14. In this manner, the lofted bomb willbe precisely delivered on the target T.

Range wind correction The range wind correction is a computed distancewhich serves to correct the still air pull-up distance from the targetT. It is the product of the total time anticipated release point.

from the pull-up point to impact multiplied by the range wind velocityor the total on-course rate correction accumulated in the PAR ZONE. Incomputing the range wind correction, it is assumed that the air moveswith the same speed and direction altitudes.

The total on-course rate correction developed by the unit 90 at itsoutput shaft 96a angularly positions the rotor of a linear transformer179 of a range wind correction unit 180. The output voltage excites alinear transformer 182 when contacts 57e, operated by the cam 57, closeat the beginning of the NEAR ZONE. The rotor of the transformer 182 isangularly positioned by the total time cam follower thereby developing avoltage on the fixed coil of the transformer 182 proportional to theproduct of the total time and the accumulated on-course rate correction.This voltage is impressed across the amplifier 92 and the stator coil ofthe transformer 91 when the contacts 57:? close. The amplifier 92 thusdrives the motor 93, shaft 96 and the rotor of the transformer 91 untilthe latters output voltage is equal to and opposite that existing on therotor coil of the transformer 182. The resultant position of the shaft96 is therefore proportional to a distance which is the range Windcorrection.

Cross wind correction for cross wind. which'degrades the loft bombingaccuracy.

Cross wind causes the bomb trajectory to bend downwind terminating at aposition laterally displaced from its The drift correction contemplatedabove in connection with the navigation computations is for providingsteering information during RUN-IN so that the aircraft 10 is on acourse aimed at the target T. When it reaches one-third mile before thepull-up zone, the yaw/ roll gyros unca'ge so that the pilot can alsocomply with the strict requirement of level wings during pull-up. Such.drift correction, however, does not produce a trajectory terminalhaving sufficiently small lateral displacement from the target as toinsure full effectiveness of the bomb. The particular steering angle atthat instant, absent cross wind correction, does not account completelyfor the effect of the cross wind on the aircraft 10 from one-third notedhereinabove, the difference between the heading angle 1 and the courseangle or is the drift angle 5; and

the steering angle 0' formed by the target angle 7' and the course anglea. The steering angle 0' is used by the pilot during RUN-IN up to onemile before the pull-up point 12; then it is desirable to yaw theaircraft at the corrected steering angle a The corrected steering angleis expressed algebraically as follows:

where or =corrected course angle The corrected course angle et isalgebraically stated as where 'q=instantaneous aircraft heading,

6=computed drift angle used for navigation during RUN- IN up to one milebefore pull-up, and

A6=incremental change in drift angle from the navigational computationnecessary for ballistic cross wind I 1 correction By definition, A6 canbe mathematically expressed as where The drift angle 5' is computed fromthe following equation:

r Wa sina'j TAs -AV cos 0dt+ TAIS cos 0, sin 5 (i -t where W cross windvelocity component,

TAS =true airspeed at pull-up point 12,

TAS =true airspeed at bomb release point 14,

AV=magnitude of velocity fall-01f from the time of computed pull-up,

0=instantaneous angle of elevation of the aircraft,

fi angle of elevation of the aircraft at release point 14,

a' drift angle for ballistic cross wind correction,

t ztime at pull-up point 12,

t =time at release,

t =time expired from pull-up to release, and

I :time expired from pull-up to impact.

The right side of the Equation 4 comprises two components: the firstbeing the lateral displacement of the aircraft from the pull-up point 12to the bomb release point 14; and the second being the lateraldisplacement of the lofted bomb in its trajectory.

distance used to shape cam 186, infra. Therefore, Equation 5 may berewritten as I: m 5 Sm Still-air pull-up distance Since the aircraft ison a heading computed from the drift angle prior to pull-up, then atpull-up point 12 TAS sin 66,

I: 5 Sm Still-air pull-up distance The still-air pull-up distance cam186, infra. has an output representing the pull-up distance with respectto the air mass. A discrepancy in the indicated and correct pull-updistances will occur whenever the TAS vector and the ground velocityvector are not aligned with the MCL; the former being slightly greater.This is because the hypotenuse of the right triangle is used as if itwere the on-course side of the triangle in the mechanized approximation.The mathematical ratio of the cross wind displacement (TAS sin fit tothe still-air pull-up distance is technically a sine function but thetangent will be substituted as an approximation whereby a smaller driftangle 6' results. Hence Sin. 51ft I -1 5 tan Still-air pull-up distancedisplacement during straight and level flight from the onethird milepoint to the pull-up point 12. These two displacements constitute anerror of overcorrection; but by using the tangent function instead ofthe sine, the computed drift 6' Will be smaller and less over-correctionwould occur from the two upwind displacements.

To anticipate further over-correction occurring during the straight andlevel flight over the last one-third mile before reaching the pull-uppoint 12, Equation 8 may be modified as follows:

I: 6 tan GS Still-air pull-up distance+% mi,

where GS=on-course component of ground speed.

TAS sin 6t Still-air pull-up distance-PX; mi.

6' =tan- (10) In the illustrated embodiment of the invention, a cam 191(to be described later in more detail) rotates proportionately with thedistance-to-pull-up whereby a follower is actuated at one mile and twothirds mile before the pull-up point 12. At the one-mile point, cam 191simultaneously closes contacts 191a-g, thereby establishing thenecessary electrical circuits for carrying out ballistic drift angle 6computations instead of navigational drift angle 6 computations.Contacts 191ag, are maintained in their last-actuated position byholding or latching means not shown.

In the illustrated embodiment of the invention, the still-air pull-updistance of Equation 10, appears on a follower shaft 241 of a still-airdistance cam 186 (FIG. 5 This shaft position predicts the pull-updistance from the target T for a particular RUN-IN speed under stillairconditions and is sensed as an angular position on the rotor of a lineartransformer 242. The stator of the transformer 242 is pre-positioned insuch a way that the output voltage thereof is proportional to thestill-air pull-up distance plus one-third of a mile. This voltage isused to excite one stator leg of the resolver 126 (FIG. 3b).

A true air speed TAS signal from transducer 37 and shaft 38 (FIG. 3a),positions the rotor of the transformer 101 in the cursor drive unit 100(FIG. 30) to produce an output voltage proportional to TAS. This voltageexcites the rotor of a linear transformer 182 (FIG. 3a) which in turn ispositioned by a follower shaft 243 of a total time cam 183. The cam 183is simply a function of a particular RUN-IN shaft speed. The output ofthe transformer 182 is therefore a voltage proportional to the productof TAS and total time t and is used to excite one stator leg of aresolver 244 (FIG. 3b); the other stator leg being left open. Theangular position of the rotor is proportional to the drift angle 6generated in the FAR ZONE and stored on the shaft 132a. The rotorvoltage from the resolver 244 is therefore a sine function of the driftangle 6; and the output voltage of the complete circuit containinglinear transformers 101 and 182 and resolver 244 is proportional to theproduct of TAS, t and sin 6. This voltage is used to excite the otherstator leg of the resolver 126.

The rotor coil of the resolver 126 supplies a voltage to the amplifier129 to drive the motor 131. The output of the motor 131 is coupled tothe rotor of the resolver 126 by the shaft 132, the angular position of\ghich represents the drift angle 6' when in a null conition.

Prior to the one-mile point, the output shaft132 has positioned theshaft 132a through the clutch 133 in accordance with the navigationalcomputations to represent the drift angle 6. At the one-mile point,clutch 133 is opened and the shaft 132a is locked. A clutch 246 alsocloses to establish an input to a mechanical differential 247 through ashaft 1321). A flyback spring 248 on the shaft 132k restores a zeroangle position at the completion of the bombing mission. The other inputto the differential 247 is derived from the navigational drift angle 6stored on the shaft 1320. The differential 247 carries out Equation 3 byalgebraically subtracting 6 from 6' to produce an output signal on ashaft 249 which is equal to the incremental drift angle A6. The rotor ofaresolver'251'is'angularly positioned by the shaft 249:

One stator leg of the resolver 251 is excited from a constant signalsource While the other stator leg is left open whereby the voltagedeveloped by the vrotor is proportional to sin A6. This voltage isalgebraically added to the output of the control transformer 143 so thatthe output from the motor 146 is the summation of the heading '1 and theincremental drift angle A6.. The resulting position of the shaft 147 ismathematically expressed as 1 +A6, and forms one of the inputs to themechanical differential 134. The other input to the differential 134being the navigational drift angle 6, the output position of the shaftis equal to the corrected course angle a (Equation 2). The correctedcourse angle et is algebraically added to the target angle 6- in themechanical differential 166 resulting in a corrected steering angle 0'(Equation 1) for presentation to the pilot at one mile prior to thepull-up point 12.

An alternate method of deriving the corrected steering angle o' is to beobtained by computing the incremental drift angle A6 directly toinsertion in Equation 2 supra. In order to derive an equation for theincremental drift angle A6, Equation 7 is first rewritten so that itsdenominator corresponds to the denominator in Equation 9 as follows:

TAS t (Still-air Pull-up Distanee+% mi.) Still-air Pull-up Distance+}mi.

6=sin (11) The mechanization of Equation 13 is best explained withreference to FIG. 6. The electrical contacts for establishing thecircuits as shown after the one-mile point before pull-up have not beenillustrated but it is contemplated that they would be operative in amanner similar to contacts 191a-g of the embodiment in FIG- URES 3a-b.

In FIG. 6, the angular position of the output shaft 132 is proportionalto the bracketed quantity of Equation 13. The numerator is obtained bymultiplying TAS by the total time I in the linear transformers 101 and182, and then subtracting the still-air pull-up distance plus one-thirdmile in a linear transformer. 255 therefrom. The numerator is thendividedby the still-air pull-up distance plus one-third mile in lineartransformers 256 and 257.

The resolver 126 combines the drift angle 6 from the linear transformer151 with the position of the shaft 132 yielding an output proportionalto sin A6. The incremental drift angle A6 and the heading 1; arecombined electrically .at the amplifier 144 and converted to an angularposition of the shaft 147. The navigational drift angle 6 is addedthereto in the differential 134, and

17 the output thus represents the corrected course angle a (Equation 2).The corrected steering angle a is computed in accordance With Equation 1in the differential 166, for presentation to the pilot at one mile priorto the pull-up point 12.

Pull-up point and g-programmer The shaft 96 is also mechanically coupledto one of the inputs of a mechanical differential 184 (FIG. The otherinput to the differential 184 is the angular position of the follower ofthe still air distance cam 186. The algebraic sum of the two inputs tothe differential 184 is a corrected pull-up distance from the target Tfor a particular speed and range wind condition and is represented bythe angular position of the shaft 187.

The shaft 187 from the differential 184 is connected to one input of amechanical differential 188 Where its position is subtracted from theinstantaneous map position represented by the angular position of theshaft 61 connected to another input of the differential 188. The outputshaft 189 of the differential 188 therefore represents the remainder ordistance to go to pull-up and is used for gen erating various alertingsignals. A cam 191 rotates with the output shaft 189 causing a contact192 to close momentarily at one mile and at two-thirds of a mile beforethe pull-up point thereby energizing a green warning light 193 as avisual indication to the pilot of approach to the pull-up point 12. Asignal is also initiated by a g-start cam 185 which rotates with theshaft 189 and engages the solenoid operated clutch 198 of a g-programmerunit 190 at the point one-third mile from the pull-up point. As notedpreviously, switch 171 (FIG. 3c) also moves from the position shown.Shaft 61 now drives a plurality of cams. A switch cam 199 connects a DC.electrical source to a potentiometer 291. A g-cam 197 rotates with theshaft 61 with its follower connected to the wiper arm of thepotentiometer 201 which in turn has its variable output voltageconnected to the drive coil of a horizontal pointer 176 in the indicator170. The potentiometer 261 output is characterized to cause the pointer176 first to drop, then to rise gradually, and finally to reach ahorizontal position at the precise instant of the computed pull-up point12. This pointer action provides a visible anticipatory signal forpull-up. At the point of pull-up, a cam 262, driven by the shaft 61,closes a contact 293 to connect a DC. electrical source to an audiooscillator 204 and a pullup light 206; and the g-programmer cam 197continues to rotate to drive the pointer 176 according to a desiredschedule of transition from one g to four gs transverse accelerationalong the Z-axis of the aircraft 10. The output signal from thepotentiometer 2131 opposes the output signal from the potentiometer 177at the actuating coil of the pointer 176 thereby presenting aninstantaneous g-error signal on the pointer 176. The g-transitionschedule is therefore a function of the on-course distance to the targetT, and the acceleration program throughout this distance may be variedto meet any tactical condition. For example, an S-shaped pull-up curveor acceleration versus distance curve is preferred in certainhigh-performance aircraft. When the pilot maneuvers the aircraft 14 sothat the transverse acceleration along the aircraft Z- aXis matches theoutput of the potentiometer 201, the pointer 176 remains horizontal,indicating that the proper pull-up maneuver is being executed. Anydeviation from the g-program is indicated by a deflection of the pointer176 which the pilot can correct with the control stick. Ear phones 267are provided for presenting the audible signal from the oscillator 294to the pilot. After release of the bomb, the clutch 198 is disengagedand a fly back spring 208 resets the cams in the g-programmer unit 190to its initial position prior to pull-up.

Bomb release angle As noted earlier with reference to FIG. 1, therelease angle 0 should be varied to correct for errors developed afterthe computed pull-up point. A bomb release angle unit 211 is providedfor computing the variable release angle 6 based on deviations from thepredicted fall-off of velocity during the pull-up. At the beginning ofpull-up, determined by the pull-up cam 202, solenoid operated clutches211 and 213 engage. The clutch 211 drivingly connects the timer outputshaft 87 to a differential velocity or AV cam 212 whereby it isangularly positioned in proportion to integrated time from the pull-uppoint. The shape of cam 212 produces follower motion representing thepredicted fall-off of aircraft velocity at any instant of time duringthe pull-up. The clutch 213 drivingly connects the TAS shaft 38 througha shaft 38a to one input of a mechanical differential 214. The positionof shaft 38a is not true airspeed, but the actual velocity fall-off;i.e. the difference between true airspeed and the instantaneous value oftrue airspeed at the computed pull-up point upon closing the clutch 213.The other input to the differential 214 is connected to the follower ofthe AV cam. The output shaft 216 of the differential 214 therefore isthe difference between the predicted velocity fall-off as generated bythe cam 212 and the measured velocity falloff at any instant after thecomputed pull-up. If the measured velocity fall-off and the predictedvelocity fallolf are the same, the output of the differential 214 iszero and no change in the preselected release angle 0 is necessary.However, if they differ, the shaft 216 causes rotation of a At) cam 217.The follower of the A0 cam 217 develops a quantity proportional to amodification in the preselected release angle 6 required to obtain atarget hit. The follower motion is transmitted to one input of amechanical differential 223, the other input being a preselected releaseangle 9 adjusting knob 224. The output shaft 226 of the differential 223is drivingly connected to one input of a mechanical differential 227where it is compared with another input 228 from a vertical gyro 229.The algebraic sum of these inputs appears at the output shaft 231 whichrotates a bomb release cam 232. At the precise modified bomb releaseangle 0iA6, the cam. 232 closes a contact 233 connected in series with apickle switch 236 and an electric mechanism 234. If the pilot-actuatedpickle switch 236 is closed at the time the contact 233 closes, themechanism 234 will release a bomb 237.

OPERATION The pilots role in a low-altitude, loft-bombing missionutilizing the present invention is a vital one because he is the linkwhich ties the computations and input data to geographical landmarks andhe also is the link between the output information and the aircraftperformance. Certain inputs such as TAS and magnetic heading areautomatically entered into the system Without attention from the pilot;but the on-course and cross-course corrections are supplied by the pilotas he ties in specific points in the computations to the geographicallandmarks. The display unit 26 provides a means by which the pilot canmonitor the end result of the navigational computations. The outputinformation is essentially guidance instructions or commands which reachthe pilot by visible or audible signals. The indicator provides steeringguidance up to one-third mile from pull-up; and thereafter, yaw/rollerror and gerror information for the pull-up maneuver. Warning lightsand a pull-up tone provide timing information to the pilot of guidanceevents.

Prior to a bombing mission, the strip map 20 is prepared based onintelligence information developed from reconnaissance information abouta target area. The map 20 is then loaded on a cartridge in the displayunit 26. The map angle 1 and local variations are entered by theadjusting knobs 137 and 138, respectively. The map 20 is then aligned sothat the target T lies directly under the horizontal index 34. Theclutch 62 is then engaged and the pilot slews or transports the map 20by means of the roller knob 29 until the start point S lies directlyunder the horizontal index 34. This stores the total distance 19 to thetarget T in the steering angle unit 16h. If the pilot has an estimate ofthe cross wind, he has the option of setting this value into the driftangle unit 120 with the cross wind adjusting knob 148. These settingsare possible at any time before arrival at the start point S, afterwhich the system is ready to begin a bombing mission.

Referring to the map 20 in FIG. 2, the low-altitude loft-bombingtechnique will be further described. When the start point Scharacterized by a large three-wing multist-ory building first comesintoview from the aircraft flying toward the target area, the pilotadjusts the cursor adjusting knob 116 of the drift angle unit 120 to thepredicted lateral distance from the start point S at which the aircraft10 will be when it flies abreast of the start point S. For example, 16miles to the left of the start point S, as represented by a typicalground track 238 on the map 20. Although it is preferable to have thepredicted lateral distance setting made prior to the arrival abreast ofthe start point S, there is about a l-mile leeway allowed beyond thestart point S in which interval the initial setting could still be made.When the aircraft 10 comes abreast of the start point S, the pilotdepresses the START button 80 to start the map portion and computeroperation. From this point on, the pilots task is to establish goodcomputer tracking.

When the aircraft comes abreast of each preselected ground check point1, 2, 3, 4 and 5, the pilot marks the aircraft 10 position by depressingthe MARK button 77. If the on-course component of the map position doesnot agree with that of the geographical position of the aircraft 10 atthat instant, that is, if the check point printed on the map is notunder the horizontal index 34, two types of corrections occur. One isthe step correction or skip of the map which brings the on-coursecomponents of the map position into alignment in both the NEAR and FARZONES. The other is the on-course rate correction which synchronizesaircraft speed in the FAR ZONE with the map speed. After about threemarks in the PAR ZONE, correct on-course tracking is established. Asnoted before, an inadvertent omission of a mark at any of the checkpoints is not harmful to the accuracy of the computation. Trackingcontinues in accordance with the corrective information accumulated upto the last marked check point.

From the start point S, tracking in the cross-course direction dependsupon the initial lateral setting of the cursor 31, the estimated crosswinds setting, and the automatic inputs of the compass 145 and TAStransducer 37. Corrected cross-course tracking is subsequently added.There being no preselected lateral check points, the pilot selects hisown. A straight section of railroad or highway running in the samegeneral direction as the line of flight makes an excellent lateral checkpoint. For example, in map the substantially parallel portion of highwaybetween 50 and 52 miles from the target T in the PAR ZONE is estimatedas 7 miles to the right of the aircraft 10 within that region. The pilotadjusts the cursor adjusting knob 116 so that the cross-course componentof the map position agrees with his estimated geographical position, andthen he presses the lateral drift button 122 thereby entering a lateralcorrection into the drift angle unit 120. The drift angle 6 is computedand is further combined with the heading 1 to obtain the tracking asdescribed above. After about two such lateral estimates in the PAR ZONE,correct tracking in the lateral direction is established.

The shaded area 21 on the map 20 alerts the pilot to an impending changein map scale. The aircraft It) must not be tracking in the area 21 whenthe map 20 changes from the PAR ZONE scale to the NEAR ZONE scale.Otherwise the ground track line 238 will be lost beyond the laterallimits of the map 20 in the NEAR ZONE.

Once in the NEAR ZONE, the pilot marks at least once more before thepull-up maneuver. At one mile from the computed pull-up point 12, thegreen alert light 193 flashes and the RUN-IN steering angle 0' indicatedon the vertical index 168 changes to a corrected steering angle a Thepilot must then reorient the aircraft yaw to correspond to the newcommand in order to offset the effects of the cross wind on the aircraftafter one-third mile before pull-up and on the bomb during itstrajectory from time of release to impact. At two-thirds of a mile fromthe pull-up point 12, a second warning is given bythe same light 193. Atthis point the pilot should begin to level the wings of the aircraft 10.At one-third of a mile from the pull-up point 12, the presentation onthe vertical pointer 168 is changed from the corrected steering angle oto a combined signal of yaw and roll error. The horizontal pointer 176,which was horizontal just prior to the one-third mile point, dropsabruptly and begins to rise gradually toward the horizontal position asthe pullup point 12 is approached. This rise represents a visiblewarning of the pull-up point 12. Between the one-third mile point andthe pull-up point, the pilot should depress the pickle button 236. Whenthe horizontal pointer 176 reaches zero, this signifies to the pilot hisarrival at the computed pull-up point. In addition, the red indicatorlight 206 is turned on and an aural tone is presented to the pilotthrough the earphones 207. From this point on, the horizontal pointer176 presents a programmed pull-up in terms of g-error. The accelerationtransition in the illustrated example in FIG. 1 from one to four gsfollows a negative cosine function of the ground distance traveled fromthe pull-up point 12. The four glevel is reached at a point which isabout one-third of a mile after the pull-up point 12. Therefore, thepilot must apply full throttle and pull back on the control stick toaccelerate the airplane in accordance with the programmed G schedule. Solong as the pilot keeps the horizontal pointer 176 horizontal he isproperly controlling the transverse acceleration forces. Maintaining thevertical pointer 168 in a vertical position, thereby maintaining thewings of the aircraft 10 level during the pull-up, is imperative for anaccurate bomb delivery.

During the pull-up maneuver, bomb release in automatically elfected bythe bomb release angle unit 210 without any attention from the pilot.However, bomb release may be signaled to the pilot by the red light 206going out and the aural tone stopping. After bomb release, the yaw-rollindication is preserved until the pickle button 236 is released. Thepilot then continues on an inside loop and half-roll to maneuver theaircraft away from the target T.

It will be observed that during the run-in phase and the pull-upmaneuver, the pilot is presented with certain information. As a resultof operation on monitored inputs plus pilot corrections, the computersystem computes and presents a continuous track of the instantaneous mapposition on the display unit 26. The knowledge of the present positionin relation to terrain features shown on the map 20 is very helpful forthe recognition of corresponding terrain features on the ground,particularly of the check points 1, 2, 3, 4 and 5. Obstacle avoidance isanother benefit of tracking information. The knowledge of presentposition in relation to future positions is also useful navigationalinformation. For example, if the trend of the successive map positionsforetells of possible entrance into the shaded area 21 on the map 20,the pilot can take appropriate action to avoid that area. Within theNEAR ZONE, the curved lines 22 guide the pilot into the region where theballistic computations are valid. If the ground track indicates itspossible intersection with one of these lines, the pilot knows that thisintersection is the last point along that particular ground track fromwhich he could maneuver by two successive standard rate turns into theregion where the ballistic computation is valid.

Another type of information to the pilot is the steering angle 0'. Thesteering angle 0- is presented on the vertical pointer 168 of theindicator 170 from the start point S up to one-third of a mile frompull-up point 12. Thus, the steering angle presents valuable guidanceinformation to the pilot for directing the aircraft lit to the target T;and at one-third of a mile from pull-up the indicator 170 is responsiveto the yaw and roll to aid the pilot in leveling the wings of theaircraft 10.

The apparatus of the present invention has novel features which departfrom devices heretofore used in low-altitude loft-bombing techniques.Several of the important features of the navigational computer may benoted, such as a moving-map type of navigational aid which includesample check points to eliminate the high dependence upon a singleinitial point, continuous ground tracking of the map position, steeringto a target Within a relatively Wld approach corridor, and permissibleWide variations in aircraft run-in speeds. The ballistic computeraffords a variable pull-up point depend ent upon a variable run-in speedand range wind, a steering signal to the pilot for orienting theaircraft to offset the effects of cross Wind on both the aircraft andthe bomb, a programmed transition of transverse acceleration duringpull-up, and a modification of the bomb release angle based ondeviations in fall-off of velocity from the ideal to compensate forvarious errors accumulated after pull-up. Due to these features thelow-altitude loft-bombing technique has been improved over the currenttechniques to the extent of greater reliability and accuracy of deliveryof the bomb on a target, greater flexibility in maneuvering of theaircraft, and less demand on pilot skill and acuity.

It will be understood that various changes in the details, materials,steps and arrangement of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art Within the principle and scope of theinvention as expressed in the appended claims.

What is claimed is:

1. Steering correcting computing means for use in loft-bombing missionby an aircraft, comprising: combining means responsive to signalsproportional to true airspeed of the aircraft, a computed time from thepullup of the aircraft to impact of the bomb, a predicted stillairpull-up distance, a preselected distance before the pull-up point, andthe navigational drift angle, for producing an incremental drift anglecorrection signal at the output thereof; summing means having one inputconnected to the output of said combining means and the other inputresponsive to a signal proportional to aircraft heading; firstdifferential means having one input connected to the output of saidsumming means and the other input responsive to a signal proportional tonavigational drift angle; second differential means having one inputconnected to the output of said first differential means and the otherinput responsive to a signal proportional to target angle; and steeringindicating means having the input thereto connected to the output ofsaid second differential means; whereby a command signal is presented tothe pilot of a corrected steering angle.

2. Steering correcting computing means for use in loftbombing mission byan aircraft, comprising: combining means responsive to signalsproportional to true airspeed of the aircraft, a computed time from thepull-up to impact, a predicted still-air pull-up distance, a preselecteddistance before pull-up point, and the navigational drift angle, forproducing an incremental drift angle correction signal at the outputthereof; summing means having one input connected to the output of saidcombining means and the other input responsive to a signal proportionalto aircraft heading; differential means having one input connected tothe output of said summing means and the other inputs responsive tosignals proportional to navigational drift angle and the target angle;and steering indicating means having the input thereto connected to theoutput of said differential means; Whereby a command signal is presentedto the pilot of a corrected steering angle.

3. Steering correcting computing means for use in loftbombing mission byan aircraft, comprising: first means for generating a signalproportional to the true airspeed of the aircraft; first computing meansconnected to said first generating means for producing an incrementaldrift angle correction signal at the output thereof; second means forgenerating signals proportional to aircraft heading, navigational driftangle, and target angle; second computing means having one inputconnected to the output of said first computing means and the otherinputs connected to said second generating means, and indicating meanshaving the input thereto connected to the output of said secondcomputing means.

4. A steering correction computer for use in a loftbombing mission by anaircraft, comprising: first multiplier means having one input responsiveto a signal proportional to true airspeed of the aircraft and anotherinput responsive to a signal proportional to a computed time frompull-up of the aircraft to impact of the bomb, first converting meanshaving an input responsive to a signal proportional to navigationaldrift angle for producing a sine function signal at the output thereof,second multiplier means having one input connected to the output of saidfirst multiplier means and the other input connected to the output ofsaid first converting means, first summing means having one inputresponsive to a predicted still-air pull-up distance and the other inputresponsive to a signal proportional to a predetermined distance beforepull-up, dividing means having a numerator input connected to the outputof said second multiplier means and a denominator input connected to theoutput of said first summing means, second converting means having aninput connected to the output of said dividing means for producing asignal proportional to the arc tangent of the input signal at the outputthereof, first differential means having one input connected to theoutput of said second converting means and the other input responsive toa signal proportional to navigational drift angle, second summing meanshaving one input connected to the output of said first differentialmeans and the other input responsive to a signal proportional toaircraft heading, second differential means having one input connectedto the output of said second summing means and the other inputresponsive to a signal proportional to navigational drift angle, thirddifferential means having one input connected to the output of saidsecond differential means and the other input responsive to a signalproportional to target angle, and steering indicating means having theinput thereto connected to the output of said second differential means;whereby a command signal is presented to the pilot of the correctsteering angle.

5. A steering correction computer for use in a loftbombing mission by anaircraft, comprising: first computing means having inputs responsive tosignals proportional to true airspeed of the aircraft, a computed timefrom pull-up to impact, and the navigational drift angle; first summingmeans having one input responsive to a predicted still-air pull-updistance and the other input responsive to a signal proportional to apredetermined distance before pull-up; dividing means having a numeratorinput connected to the output of said first computing means and adenominator input connected to the output of said first summing means,converting means having an input connected to the output of saiddividing means for producing a signal proportional to the arc tangent ofthe input signal at the output thereof; first differential means havingone input connected to the output of said converting means and the otherinput responsive to a signal proportional to navigational drift angle;second summing means having one input connected to the output of saidfirst differential means and the other input responsive to a signalproportional to aircraft heading; second differential means having oneinput connected to the output of said second summing'means and the otherinputs responsive to signals proportional to navigational drift angle,and the tangent angle; and steering indicating means having the inputthereto connected to the output of said second differential means;whereby a command signal is presented to the pilot of the correctsteering angle.

6. A steering correction computer for use in a loftbombing mission by anaircraft, comprising: first computer means having inputs responsive tosignals proportional to true airspeed of the aircraft, a computed timefrom pull-up to impact, and the navigational drift angle; summing meanshaving one input responsive to a signal "proportional to a predictedstill-airpull-up distance and the other input responsive to a signalproportional to a predetermined distance before pull-up; secondcomputing means having inputs connected to the output of said firstcomputing means and the output of said summing means; third computingmeans having one input connected to the output of said second computingmeans and the other inputs responsive to signals proportional tonavigational drift angle, the aircraft heading, and the target angle;and steering indicating means having the input thereto connected to theoutput of said third computing means; whereby a command signal ispresented to the pilot of the correct steering angle.

7. Steering correcting computer means for use in a loft-bombing missionby an aircraft, comprising: first multiplier means having one inputresponsive to a signal proportional to true airspeed of the aircraft andthe other input responsive to a signal proportional to a computed timefrom pull-up of the aircraft to impact of the bomb, first summing meanshaving one input responsive to a signal proportional to a predictedstill-air pull-up distance and another input responsive to a signalproportional to a preselected distance before pull-up, substractingmeans having one input responsive to the output of said first multipliermeans and the other input responsive to the output of said first summingmeans, dividing means having a numerator input connected to the outputof said substracting means and a denominator input connected to theoutput of said first summing means, second multiplier means having oneinput connected to the output of said dividing means and the other inputresponsive to a signal proportional to navigational drift angle, secondsumming means having one input connected to the output of said secondmultiplier means and the other input responsive to a signal proportionalto aircraft heading, first differential means having one input connectedto the output of said second summing means and the other inputresponsive to a signal proportional to navigational drift angle, seconddifferential means having one input connected to the output of saidfirst differential means and the other input responsive to a signalproportional to target angle, steering indicating means having the inputthereto connected to the output of second differential means; whereby acommand signal is presented to the pilot of a corrected steering angle.

8. Steering correcting computer means for use in a loftbombing missionby an aircraft, comprising: computing means having inputs responsive tosignals proportional to true airspeed of the aircraft, a computed timefrom pullup to impact, a predicted still-air pull-up distance, and apreselected distance before pull-up; multiplier means having one inputconnected to the output of said computing means and the other inputresponsive to a signal proportional to navigational drift angle signal;summing means having one input connected to the output of said computingmeans and the other input responsive to a signal proportional toaircraft heading; differential means having one input connected to theoutput of said summing means and the other inputs responsive to signalsproportional to navigational drift angle and the target angle; andsteering indicating means having the input thereto connected to theoutput of said differential means.

9, Steering correcting computer means for use in a loftbombing missionby an aircraft, comprising: first means for generating signalsproportional to the true airspeed of the aircraft and a computed timefrom pull-up to impact of the bomb; first computing means connected tosaid first generating means for combining said signals; second means forgenerating a signal proportional to navigational drift angle; multipliermeans having one input connected to the output of said first computermeans and the other input to said second generating means; third meansfor generating signals proportional to the aircraft heading,navigational drift angle, and target angle; second computing meanshaving' one input connected to the output of said multiplier means andthe other inputs corrected to said third generating means; and steeringindicating means having the input thereto connected to the output ofsecond computing means.

It A ballistic computer for use in a loft-bombing mission by anaircraft, comprising: variable pull-up point computing means including,first multiplier means having one input responsive to a signalproportional to range wind velocity and another input responsive to asignal proportional to a computed total time anticipated from pull-uppoint to impact, a first differential means having one input connectedto the output of said multiplier means and another input responsive to asignal proportional to a predicted still-air pull-up distance, a seconddifferential means having one input responsive to a signal proportionalto ground speed of the aircraft and another input connected to theoutput of said first differential means, first connecting meansintermittently connecting the aircraft ground speed signal to the outputof said second differential, first indicating means, and secondconnecting means intermittently connecting the output of said firstconnecting means to the input of said first indicating means; pull-upprogrammer means including scheduling means having an input connected tothe output of said first connecting means, comparator means having oneinput operatively connected to the output of said scheduling means andanother input responsive to a signal proportional to verticalacceleration of the aircraft, second indicating means for presenting aprogrammed pull-up having the input thereof connected to the output ofsaid comparator; variable bomb release angle computing means includingthird connecting means intermittently connecting a signal proportionalto true airspeed of the aircraft to the output of said second connectingmeans, first converting means for producing an output signalproportional to a predicted fall-off velocity signal of the aircraft,fourth connecting means intermittently connecting a signal proportionalto computed time to the output of said first converting means, thirddifferential means having one input connected to the output of saidthird connecting means and the other input connected to the output ofsaid first converting means, second converting means having an inputconnected to the output of said third differential means for producing abomb release angle correction signal at the output thereof, fourthdifferential means having one input connected to the output of saidsecond converting means and the other input responsive to a signalproportional to a preselected bomb release angle, fifth differentialmeans having one input connected to the output of said fourthdifferential means and the other input responsive to a signalproportional to pitch angle of the aircraft, and bomb release means forreleasing the bomb having the input thereof connected to the output ofsaid fifth differential means; and steering correction computing meansincluding a second multiplier means having one input responsive to asignal proportional to true airspeed of the aircraft and another inputresponsive to a signal proportional to a computed time expired frompull-up to impact, third converting means having an input responsive toa signal proportional to navigational drift angle for producing a sinefunction signal at the output thereof, third multiplier means having oneinput connected to the output of said second multiplier means and theother input connected to the output of said third converting means,first summing means having one input responsive to a signal proportionalto a predicted still-air pull-up distance and the other input responsiveto a signal proportional to a predetermined distance before pull-up,dividing means having a numerator input connected to the output of saidthird multiplier means and a denominator input connected to the outputof said first summing means, fourth converting means having an inputconnected to the output of said dividing means for producing the arctangent signal of the input signal at the output thereof, sixthdiiferential means having one input connected to the output of saidfourth converting means and the other input responsive to a signalproportional to navigational drift angle, second summing means havingone input connected to the output of said sixth ditferential means andthe other input responsive to a signal proportional to aircraft headingsignal, seventh differential means having one input connected to theoutput of said second summing means and the other input responsive to asignal proportional to navigational drift angle, eighth differentialmeans having one input connected to the output of said seventhdiflferential means and the other input responsive to a signalproportional to target angle, and third indicating means for presentinga corrected steering angle signal to the pilot having the input theretoconnected to the output of said eighth differential means.

11. A ballistic computer for use in a loft-bombing mission by anaircraft comprising, in combination: variable pull-up point computingmeans having a first output signal of a computed pullup point to thepilot, a second output signal of a first predetermined distance beforethe computed pull-up point, and a third output signal of a secondpredetermined distance before the computed pullup point, said secondpredetermined distance being greater than said first predetermineddistance; pull-up programmer means having an input connected to saidsecond output of said variable pull-up point computing means forpresenting a correct vertical acceleration program for pull-up; variablebomb release angle computing means having an input electricallyconnected to said first output of said variable pull-up point computingmeans for releasing the bomb at a corrected bomb release angle, andsteering correction computing means having two inputs connectedrespectively to said second and third outputs of said variable pull-uppoint computing means for presenting a corrected steering angle forpull-up.

References Cited by the Examiner UNITED STATES PATENTS 2,600,159 6/1952Ergen 235 187 2,996,268 8/1961 Brown 235187 X 3,003,398 10/1961 Lalli891.5 3,024,996 3/1962 DAmico 235187 3,070,307 12/1962 Helgeson 2351873,077,110 2/1963 Gold 235-193 3,088,372 5/1963 Brink 89--1.5 3,091,9936/1963 Brink et a1. 23561.5 3,113,170 12/1963 Mickelson 235-487 MALCOLMA. MORRISON, Primary Examiner,

K, W. DOBYNS, Assistant Examiner,

3. STEERING CORRECTING COMPUTING MEANS FOR USE IN LOFTBOMBING MISSION BYAN AIRCRAFT, COMPRISING: FIRST MEANS FOR GENERATING A SIGNALPROPORTIONAL TO THE TRUE AIRSPEED OF THE AIRCRAFT; FIRST COMPUTING MEANSCONNECTED TO SAID FIRST GENERATTING MEANS FOR PRODUCING AN INCREMENTALDRIFT ANGLE CORRECTION SIGNAL AT THE OUTPUT THEREOF; SECOND MEANS FORGENERATING SIGNALS PROPORTIONAL TO AIRCRAFT HEADING, NAVIGATIONAL DRIFTANGLE, AND TARGET ANGLE; SECOND COMPUTING MEANS HAVING ONE INPUTCONNECTED TO THE OUTPUT OF SAID FIRST COMPUTING MEANS AND THE OTHERINPUTS CONNECTED TO SAID SECOND GENERATING MEANS, AND INDICAING MEANSHAVING THE INPUT THERETO CONNECTED TO THE OUTPUT OF SAID SECONDCOMPUTING MEANS.